If the fan in the outside unit where the compressor is does not run either...no compressor and no fan outside running. Then it is likely a tripped breaker for the outside AC unit in your house breaker panel, or a tripped breaker or blown fuse in the disconnect switch located on the wall next to the outside unit.

If the fan in the outside unit is running, and just the compressor is not running, then we have to look for a high pressure cut out switch on the unit... that gets more involved, Tell me a bit about your technical background and if you have a multi meter or not, we can go from there.

it is midnight in San Francisco now, I will wait up for you though, half an hour or so, If I miss you I will be back on line in 7 or 8 hours, we can go from there.

Phil.

I hold questions open after positive ratings to allow for unlimited follow up. Please be patient though. The research & typing take time

Hello again, Its on cool 2 most likely because the house is hot and high stage cooling is being called for. lets give it some time and see how it goes tomorrow morning.

The unit tripped the breaker for a reason... a very hot day will do it. especially if the outside radiator (finned section) has dirt trapped between the fins.... a bad fan motor can also get hot and go off, that will cause the breaker to trip for a wide range of reasons.

Such a coil will look clean.... but still be clogged with dirt... it will need cleaning for sure if you are in a rural area and the unit is older than 4 or 5 years old.

To clean:Turn off the power to the unit tomorrow morning... then remove the service panels on the unit so that the outside fan and condenser coil are exposed... wrap the fan motor in plastic wrap and use a high pressure garden hose to squirt water *through* the coil so you can see it squirting out the other side.

Then remove the plastic from the motor and put the service panels back on and start the unit. Let me know how it goes.

Tell me how old the unit is please.

I will hold this question open for unlimited follow up after you rate my service to you so far *positively.

unit is 18 months old, just had AC serviced including fin leaf and dirt flush, this is a top of the line unit which hit all factory specs on service checkout, we had a 105 degree day here in Austin and been above 100 for the past week with more coming for the next 4-6 weeks.

Customer:replied 2 years ago.

We are back to just cool this morning. What are your thoughts on the nest learning thermostat?

Hello again, the NEST thermostat has proven reasonably reliable in use. That does not mean they never fail however. The chances that this is a thermostat problem are in the 1 percent range or less.... that is because the unit tripped a breaker last night, a thermostat problem will not cause that... but hot weather will.

In 105 deg F weather is it is not at all uncommon for the sun to shine on the breaker box mounted on the wall next to the unit..... then at the same time the utillity power grid for your part of the country gets over loaded and there is a 'brown out'.... a brown out is low voltage. Low voltage causes the unit to draw too many amps and that causes the breaker to trip.

That condition is also very hard on the units compressor and can burn them out.... there are after market protective devices that shut the air conditioner off in very hot weather when there is a brown out. The devices cost about $200 and labor to install is $100 or so. Maybe 2 to 5% of the air conditioners in Texas have those attached.

The chances that low voltage and a hot day are at the root of the problem in this case are close to 100%

Let me know if that makes any sense on your end or not, we can keep discussing this and various options as you need to.

Regarding the " voltage monitor and cut off" I mentioned, You can fit that into the unit if done properly without voiding the warranty in most cases. However this should be purchased locally, at an air conditioning and refrigeration wholesaler by the service people so that it can be properly selected and wired.

A home owner can make mistakes...or.... anyone seeking to void your warranty can use that as excuse to void your warranty. So it should be done professionally.

If your service contractor is not familiar with these devices you need another service contractor who is up to speed on these issues...

You can also buy a class 2 multi meter (with a 240 volt scale on it) cost about $30 and use it to check the voltage at the disconnect switch on the wall next to the condensing unit **during the time it starts on a very hot day** tell me how low the voltage dips during that attempted start attempt.. and what the voltage reads after the unit is running.. compare that voltage read to the voltage listed on the name plate of the unit.

Let me know the results, we can go from there if you have already rated my responses *positively. I hold questions open with no time limit in those cases.

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